Circular waveguide formed from a flexible ribbon carrying a conductor pattern

ABSTRACT

Circular waveguide is formed from a flexible wiring carrier or ribbon. An appropriate conductor pattern is printed on a dielectric ribbon, such as mylar tape, to form the ribbon. The ribbon may also contain layers of lossy material on one side, thereof. The ribbon is continuously wrapped transversely about a mandrel to form a longitudinal seam. The wrapped ribbon is drawn from the mandrel, cured, and encased with a protective sheath. Various types of circular waveguide, such as spaced-ring helix or solid waveguides, each having the option of a dielectric lining, may be fabricated by the same principles.

0 United States Patent 1111 3,599,126

472] Inventor Nkholas Osifthll 3,331,075 7/1967 Moulton 1 i 1 333/84 X Klanelon, NJ. 3,433,043 '3/1969 Vermeulen et a1 72/363 121] Appl. No. 864,662 2,966,643 12/1960 Kohman et a1... 333/95 [22] Filed Oct.8, 1969 2,998,047 8/1961 Mally etal. 72/368 [45] Patented Aug. 10, 1971 FOREIGN PATENTS 1731 1,087,196 8/1960 Germany 333/95 984,482 2/1965 Great Britain .4 29/600 OTHER REFERENCES Meier et a1. Dielectric-Lined Circular Waveguide with In- [54] CIRCULAR WAVEGUIDE FORMED RQM A FLEXIBLE RmBoN CARRYING ACONDUCTOR creased Usable Bandw1dth, MTT l2, 3 1964, PP 171 174 PATTERN Primary Examiner-H. K. Saalbach 4 CW 3 [)rgylng Fig Assistant Examiner-Wm. H. Punter [52] US. Cl 333/95, Almmeys Guemher and Edwm Cave 29/600, 333/31 A [51] lnt.Cl Jlfllp 11/00 ABSTRACT; Circular waveguide is f d f a fl ibl p 3/12 wiring carrier or ribbon. An appropriate conductor pattern is 0f serch printed on a dielectric ribbon such as mylar ape to form the A, 31 C, 31 A; 72/368, 370; 29/600, 601; 174/108, ribbon. The ribbon may also contain layers of lossy material 109, 36, 102, 1 on one side, thereof. The ribbon is continuously wrapped transversely about a mandrel to form a longitudinal seam. The [56] Rdennw CM wrapped ribbon is drawn from the mandrel, cured, and en- UNITED STATES PATENTS cased with a protective sheath. Various types of circular 2,697,772 12/1954 Kinghom 174/102 X waveguide, such as spaced-ring helix or solid waveguides, 3,011,933 12/ 1961 Barnes et a1. 174/102 X each having the option of a dielectric lining, may be fabricated 3,056,710 10/1962 Rose 333/95 X by the same principles.

g ggULAR WAVEGUIDE FORMED FROM A FLEXIBLE RIBBON CARRYING A CONDUCTOR PATTERN BACKGROUND OF THE INVENTION This invention relates to electromagnetic wave transmission systems and, more particularly, to apparatus and methods for making circular waveguide on a continuous or mass production basis.

Waveguide transmission lines are now deemed feasible as extremely broad frequency band transmission media for long distance communication systems. A major problem in establishing a waveguide communication network is the lack of waveguide which can be fabricated on a mass production or continuous basis. For example, circular helical waveguide typically is fabricated by winding individual strands of wire on a precision removable mandrel to form discrete sections of waveguide usually less than 20 feet in length. It is clear from the standpoint of time and economics that this is an unsatisfactory method of fabricating the thousands of miles of waveguides that may be required for a waveguide communication network. Additionally, the use of relatively short sections of waveguide greatly increases the number of couplings required in a network. Such couplings increase the losses and distortion in a system and are the source of a disproportionate amount of the trouble arising in a communication system.

It is therefore an object of the present invention to improve the apparatus and methods for fabricating circular waveguide to bemore amenable to mass production techniques.

Another object of the-invention is to provide apparatus and methods for fabricating circular waveguide on a continuous basis.

Another object of the invention is to make the fabrication of circular waveguide amenable to printed circuit techniques.

SUMMARY OF THE INVENTION In accordance with the principles of the invention an appropriate conductor pattern is printed on a dielectric ribbon such as mylar tape. Layers of lossy material are placed on the opposite side of the ribbon. The ribbon is then wrapped transversely around a mandrel to form a longitudinal seam therein. The wrapped ribbon is continuously drawn from the mandrel, cured, and encased with an appropriate protective sheath such as a thin metal sheet. The waveguide thus formed may be cut into sections of desired length or rolled onto a drum if materials of proper flexibility have been used to encase the wrapped ribbon. Different types of waveguide such as helical, solid, or spaced-ring waveguide may be formed by utilizing the same basic principles and by varying the conductor pattern on the dielectric ribbon.

DESCRIPTION OF THE DRAWINGS The objects and features of the invention may be more fully comprehended from the following detailed description and attached drawing in which:

FIG. 1 is a perspective view of a printed circuit ribbon useful in fabricating a circular spaced-ring waveguide in accordance with the invention;

FIG. 2 is a sectional view of a waveguide that has been formed from the ribbon of FIG. I; and

FIG. 3 is a schematic representation of a method for making circular waveguide according to the principles of the invention.

DETAILED DESCRIPTION On a major surface of the tape 10 a series of spaced conductive strips such as strip 11 is formed. These strips may advantageously be formed or printed by printed circuit techniques known in the art. The center-to-center spacing between adjacent conductive strips ,1] depends in part upon the frequency of signal to be transmitted. This center-tocenter spacing is usually a few mils. The spacing between the edges of adjacent strips 11 depends in part upon the desired capacitance and is usually a few mils. .On the opposite side of the tape 10 from the conductive strips 11, a layer 12 of lossy material is formed. The layer 12 of lossy material is usually much thicker than the tape 10 or conductive strips 11. Thus the relative thickness shown in FIG. 1 are not representative.

The particular configuration of the conductive strips 11 shown in FIG. 1 is useful in fabricating spaced-ring or disc circular waveguide. When the ribbon l l) lis formed into the configuration shown in FIG. 2, the ends of each' strip 11 are joined together to form a series of spaced, ringlike conductors in the waveguide. Helical circular waveguide could be readily fabricated by utilizing a ribbon l0 l having conductive strips 11 oriented diagonally across the mylar tape 10. In such case the ends each strip 11 are joined to an end of the two adjacent strips to form a continuous helical conductor in the waveguide. Solid waveguide could be fabricated by utilizing a ribbon mhaving a continuous conductive sheet instead of the discrete conductive strips 11. A dielectric lined waveguide can be obtained by depositing a dielectric layer such as a layer of mylar across the top of the conductive strips 11, or conductive sheet in the case of the solid circular waveguide. Such a dielectric lining tends to minimize the effects of dimensional inaccuracies on the surfaces of the conductive strips 11 but may also increase the loss in the waveguide.

The edges of the ribbon ill are shaved or tapered to facilitate a close fit and smooth joint when the ribbon is formed into a circular configuration shown in FIG. 2. The close fit and smooth joint will minimize signal losses in the waveguide. The shaved edges of the ribbon mpermit the conductive strips 11 to be joined at a longitudinal seam 13 without presenting major surface irregularities to the signal. Further, the shaved edges permit a large area of contact between the two ends of the formed ribbonlQl along intersection I4 whereby a strong adhesive bond may be obtained. The ends of ribbon LQL may advantageously be joined to form the waveguide by spot-welding the conductive strip intersections along seam 13 and by using an appropriate adhesive along intersection 14.

FIG. 2 shows the conductive strips continuing past the seam 13 to the exterior of the formed waveguide. If desired the conductor pattern could be terminated near the seam 13 with only the tape 10 and lossy layer 12 continuing along intersection 14 to the exterior of the waveguide.

FIG. 3 illustrates a method of making a circular waveguide on a continuous basis beginning with a ribbon such as printed circuit ribbonm A continuous printed circuit ribbon I6 is formed by printed circuit techniques known in the art and placed upon an appropriate supply reel 15. The ribbon 16 is taken from reel 15 continuously and placed on a forming mandrel 17 similar to mandrels known in the art. Mandrel 17 might advantageously be a rotating mandrel to minimize eccentricity errors and to increase the precision of the waveguide. The rotating mandrel might advantageously be supported by a hydrostatic bearing in a concentric stationary mandrel. Further the ribbon may be supported on the rotating mandrel by a hydrostatic bearing. Appropriate alignment devices known in the art are used to maintain alignment of the mandrel 17.

As the ribbon 16 is placed on the mandrel 17, a conductor alignment station 18 monitors the alignment of the conductive strips 11 on the ribbon, and adjusts the tension on the ribbon 16 to achieve proper alignment. This insures a good intersection of the conductive strips 11 along seam I3 when the ribbon is formed into the circular waveguide. The sensing of the conductor alignment may be accomplished by known devices such as optical or photoelectric devices. The tension adjustment apparatus is also known in the art.

The mandrel 17 carrying ribbon 16 passes from alignment station 18 to an adhesive applying station 19. Adhesive is applied to those portions of the ribbon 16 which intersect along intersection 14 in the formed waveguide. The mandrel 17 and ribbon 16 then pass to a forming station 20 where ribbon 16 is wrapped around the mandrel 17 to form a waveguide 30 similar to that shown in cross section in FIG. 2. The waveguide structure 30 is then taken from the forming mandrel and the conductive strips 11 are joined at their intersection along seam 13. The strip 11 may be joined by spot welding, brazing, etc., in order to obtain a good conductive joint. The

waveguide structure 30 is passed through a curing tunnel where the adhesive bond along intersection 14 is cured.

It has been found desirable and even necessary to protect the waveguide from external mechanical and electrical influences. Thus the waveguide leaving the curing tunnel 22 is sheathed with a protective metal jacket. This might advantageously be accomplished by using a metal structure which is unfurlable from ribbon form into a tubular shape such as the structure disclosed in 0.5. Pat. No. 3,331,075, issued July ll, 1967, to S. W. Moulton. The metal sheet 31 which is wound on supply 23 in ribbon form is continuously unfurled about the waveguide 30. The forming station 24 properly forms the sheet 31 around the waveguide. The sheet is then welded along a longitudinal seam at welding station 25 to form a hermetic jacket about the waveguide.

The jacketed waveguide 32 may be cut into sections of any desired length at cutting station 26. The section length can be optimized for a particular job if desired to minimize the number of couplings required. After being cut to the desired lengths, the sections of waveguide pass to an inspection and alignment station 27 where any imperfections such as eccentricity in the waveguide are corrected. Correction of imperfections such as eccentricity might advantageously be accomplished by a magnetic pulse forming head on the exterior of the waveguide and a hydraulically expandable mandrel on the interior thereof. Couplers are attached to the ends of the waveguide sections at coupler attaching station 28. The attachment of the couplers can be made by apparatus known in the art. The waveguide sections with couplers attached are taken from station 28 and used directly or prepared for shipment.

The disclosed method of making waveguide could readily be adapted to making flexible waveguide which could be reeled in indefinite lengths. For fabricating flexible waveguide the lossy layer 12 could be a flexible plastic which would be extruded on the ribbonflas the first step of the fabricating process. The protective jacket would be a corrugated metallic jacket instead of the smooth metallic sheath disclosed above.

The apparatus and method for making waveguide disclosed above is merely illustrative of the principles of my invention. Therefore, it is to be understood that various modifications thereto might be made by those skilled in the art without departing from the spirit and scope of my invention.

What I claim is:

1. A circular waveguide comprising, in combination, an elongated dielectric ribbon member having a plurality of conductive strips on a first major surface and an electrically lossy layer on a second major surface thereof, said member being formed into a substantially tubular structure with said lossy layer on an exterior surface thereof so as to form a longitudinal seam therein, said ribbon member having tapered edges such that a relatively large area of contact between said edges can be obtained along said longitudinal seam,- and means for joining the edges of said ribbon member along said longitudinal seam.

2. Apparatus in accordance with claim 1 wherein said conductive strips are oriented substantially perpendicular to said edges of said ribbon member, each of saidconductive strips having the ends thereof conductively joined, thereby to form a spaced-ring circular waveguide.

3. Apparatus in accordance with claim 1 wherein said conductive strips are oriented at an angle of less than with respect to said edges of said ribbon member, each of said conductive strips having first and second ends conductively joined to one end of first and second adjacent strips respectively thereby to form a circular helix waveguide.

4. A circular waveguide comprising, in combination, an elongated dielectric ribbon member having a plurality of conductive strips on a first major surface and an electrically lossy layer on a second major surface thereof, said member being formed into a substantially tubular structure with said lossy layer on the exterior surface thereof so as to form a longitudinal seam therein, and means for joining the edges of said ribbon along said longitudinal seam, said joining means including first means for conductively joining the ends of said conductive strips thereby to form continuous conductors within said tubular structure. 

1. A circular waveguide comprising, in combination, an elongated dielectric ribbon member having a plurality of conductive strips on a first major surface and an electrically lossy layer on a second major surface thereof, said member being formed into a substantially tubular structure with said lossy layer on an exterior surface thereof so as to form a longitudinal seam therein, said ribbon member having tapered edges such that a relatively large area of contact between said edges can be obtained along said longitudinal seam, and means for joining the edges of said ribbon member along said longitudinal seam.
 2. Apparatus in accordance with claim 1 wherein said conductive strips are oriented substantially perpendicular to said edges of said ribbon member, each of said conductive strips having the ends thereof conductively joined, thereby to form a spaced-ring circular waveguide.
 3. Apparatus in accordance with claim 1 wherein said conductive strips are oriented at an angle of less than 90* with respect to said edges of said ribbon member, each of said conductive strips having first and second ends conductively joined to one end of first and second adjacent strips respectively thereby to form a circular helix waveguide.
 4. A circular waveguide comprising, in combination, an elongated dielectric ribbon member having a plurality of conductive strips on a first major surface and an electrically lossy layer on a second major surface thereof, said member being formed into a substantially tubular structure with said lossy layer on the exterior surface thereof so as to form a longitudinal seam therein, and means for joining the edges of said ribbon along said longitudinal seam, said joining means including first means for conductively joining the ends of said conductive strips thereby to form continuous conductors within said tubular structure. 